COFs on MOFs: Layer-by-Layer Synthesis of MOF@COF Nanoparticles with Synergistic Adsorption.

Synergistic effects between porous materials offer a powerful route to enhance key functionalities such as adsorption, catalysis, and molecular transport. In this context, the combination of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) provides a promising platform for engineering hybrid adsorbents with synergistic sorption behavior. Here, a versatile layer-by-layer strategy is presented for the controlled growth of crystalline COF shells on MOF nanoparticles, yielding uniform MOF@COF nanocomposites as stable aqueous colloids. This approach enables precise tuning of shell thickness and porosity under mild conditions. The resulting core-shell hybrids exhibit enhanced water adsorption, driven by the formation of interfacial mesopores. Modeling studies indicate that a minimum number of COF growth cycles is necessary to induce these mesopores, which interconnect with the intrinsic micropores of the COF shell and facilitate synergistic uptake. This work presents a scalable and modular approach to creating porous hybrid nanoparticles with programmable interfacial architectures and enhanced sorption performance.